|Numéro de publication||US5345448 A|
|Type de publication||Octroi|
|Numéro de demande||US 08/052,779|
|Date de publication||6 sept. 1994|
|Date de dépôt||26 avr. 1993|
|Date de priorité||27 avr. 1992|
|État de paiement des frais||Caduc|
|Autre référence de publication||DE69313913D1, DE69313913T2, EP0568212A2, EP0568212A3, EP0568212B1|
|Numéro de publication||052779, 08052779, US 5345448 A, US 5345448A, US-A-5345448, US5345448 A, US5345448A|
|Cessionnaire d'origine||Nokia Mobile Phones Ltd.|
|Exporter la citation||BiBTeX, EndNote, RefMan|
|Citations de brevets (8), Référencé par (150), Classifications (7), Événements juridiques (6)|
|Liens externes: USPTO, Cession USPTO, Espacenet|
The present invention relates to a procedure for the handover of a radio connection between two base stations in a radio communications network.
The present invention particularly relates to a handover operation in a Time Division Multiple Access (TDMA) digital cellular radio communication system comprising a plurality of Base Transceiver Stations (BTS), and a number of Mobile Stations (MS).
Analog mobile phone systems have long been available, the basic notion thereof being that a network is composed of a plurality of mutually defined cells, each provided with a Base Station in which the transmission power covers the range of said cell, but scarcely extending to the range of an adjacent cell. The system also includes Mobile Services Switching Centers, with each of which being connected a great number of Base Stations. In addition, the system includes a plurality of mobile phones, usually called Mobile Stations (MS), so that a connection can be formed between two mobile phones or between a subscriber connected to the Public service telephone network (PSTN) and a mobile phone. Said networks are frequency divided, whereby one connection always engages two frequencies. The completely digital systems based on TDMA represent the next step of development in mobile phone systems in which the same frequency is used in several connections but at different periods of time. Of such systems may be mentioned the GSM currently being adopted into use in Europe and the digital cellular system to be used in the USA.
In all cellular networks measures have to be taken in one way or another to enable a mobile phone to move from one channel to another during a call without breaking the connection. A channel change, i.e. handover, can be intracellular, whereby the movement is made from one channel or time interval to another while remaining within one Base Transceiver Station, or intercellular, so that the connection changes to another Base Transceiver Station, this being subjected to either the same Base Station Controller or the Base Transceiver Station is subjected to a second Base Station Controller. Potential cases are shown in FIG. 1 illustrating the principle block diagram of a typical digital system. As shown therein, several Base Station Controllers BSC have been connected to a Mobile services switching centre MSC, each controlling a number of Base Transceiver Stations BTS. Each BSC together with the Base Stations connected thereto makes up a Base Station System BSS in which the control of a cellular network has been concentrated in the BSC.
A connection with other networks, such as the PSTN, is carried out through MSC. The handover can be made intracellularly, whereby a Mobile Station MS is in connection with one and the same Base Station (e.g. BTS 1) but it changes the frequency or the time interval of the trafficking channel if the level of interference on a certain channel has become too great. The handover decision is usually made in the BSC. Said intracellular handover is indicated by a. When changing a connection from one Base Transceiver Station (e.g. BTS 1) to another Base Transceiver Station (e.g. BTS 2) subjected to the same Base Station controller, the handover decision is made also in the BSC 1. Said move is illustrated by arrow b. A connection may also be moved as shown by arrow c from a Base Transceiver Station (e.g. BTS 3) to a Base Transceiver Station (e.g. BTS 21) subjected to another Base Station Controller (e.g. BSC 2). Now, the control of the move is carried out by the Mobile Services Switching Center (MSC).
A great number of measures are required in carrying out a perfect handover in prior art digital time divided radio phone systems. A Mobile Station MS must measure, not only the signal strength of the Base Station to which it is connected but also those of the adjacent Base Stations and to transmit measuring results to the Base Transceiver Station BTS in use at that moment. The Base Station transmits the data to an MSC which makes the decision on which Base Transceiver Station the call is to be transferred. In addition to measurements concerning the signal strengths of the adjacent Base Stations, the mobile station is required from time to time to discharge a given burst transmitted by the adjacent Base Stations, on the basis of which the telephone calculates the timing difference between the Base Station to which is connected and the timings of the adjacent Base Stations using the parameters derived from said Base Stations. Similarly, the frame number difference between the Base Stations in use own and the adjacent Base Stations has to be calculated.
Also the timing of starting a transmission detected by the Base Station has to be taken into account so that the synchronization with the Base Station can be maintained while the Mobile Station is moving at a long distance from the Base Station.
As a result of the measurements carried out by the Mobile Station and the Base Station, the mobile phone network determines the handover moment and to which new Base Station the connection is going to be moved. All of said operations related to the handover between the MSC, the BTSs and the Mobile Station MS require a great number of signalling and signal processing operations in the network. Therefore, in digital networks known in the art the handover operation is bound to be rather complicated and heavy.
In TDMA systems of prior art, the multiple access propagation of a signal in a radio channel is seen in the form of mutual influence between the detected bits, and the changing timing causes variations in the reception. The receivers are required to be able to correct said time-related variations produced in a radio channel over the length of several symbols, e.g. in the GSM system reservations have been made to correct delay dispersions up to 16 microseconds.
A procedure is disclosed for enabling a handover to be carried out simply in a digital, TDMA cellular system.
The handover according to the present invention can be applied to a TDMA cellular network as described above.
According to the present invention there is provided a procedure for the handover of a radio connection to a mobile radio station from a first base station to a second base station in a Time Division Multiple Acess (TDMA) cellular radio communications network the procedure comprising, transmitting to the second base station identification information regarding the mobile station including frequency channel information enabling tuning of the second base station to the channel in which the mobile station shall transmit, transmitting to the mobile station a handover command not including information on the timing of the second base station, and correcting for deviation in signal timing caused by a change in timing during handover.
A difference between the invention and the systems known in the art is therefore that the measurements of the timing data of the adjacent cells in the downlink direction (BTS→MS) is not required. A first basic prerequisite of a simplified handover is the propagation delays between an MS and a BS are not too great in relation to time. This means that the sum of the maximum delay dispersion of the radio channel defined for the network, through which a Mobile Station has to be able to pass, and of the greatest possible change in timing (timing difference) must be smaller than the correction ability required of the Mobile Station MS in the time level.
The maximum timing of the change is determined by the difference in cell sizes. A channel equalizer to correct the dispersion in the time level is needed both in the Base Station and in the Mobile Station. The capacity of the channel equalizer is sufficient to correct the mutual effect caused by the multipath propagation and the variations due to timing. Another basic prerequisite set for the network is that the timing differences of the Base Stations must be known, i.e. a Base Station must be informed of the difference of its own timing in comparison with the timings of the adjacent Base Stations. If the timing of the Base Stations is gliding relative to the other ones, the information on a change has to be updated.
A timing difference may also be kept at zero, whereby the clocks of the Base Stations are at the same phase. An adequate measuring required of a Mobile Station MS is that it is able to measure the signal level of the adjacent Base Transceiver Stations according to an adjacent list. Said adjacent list has been transmitted by the Base Transceiver Station of its own via a common control channel. The Base Transceiver Station BTS informs the Mobile Station MS subjected to the handover command of the frequency, the time interval to be used, (timing difference), and the frame number of the new Base Transceiver Station. Said information and the parameters required in identifying the Mobile Station are also given to the new Base Transceiver Station which is immediately prepared to receive a signal used in a normal traffic channel without any special bursts used e.g. in the GSM system. Most simply, in a handover situation the MS is merely turned into a new channel and it starts normal trafficking directly.
A decision on a handover is made, depending on the situation, either in the Base Station Controller BSC or in the Mobile Services Switching Center MSC, although the decision making element is not essential from the point of view of the handover process of the invention.
An embodiment of the invention is described below, by way of example, with reference to the accompanying drawings; in which
FIG. 1 schematically presents different handover cases,
FIG. 2 illustrates part of a network provided with two cells and a Mobile Services Switching Center,
FIG. 3 illustrates different delay instances related to a channel corrector,
FIG. 4 shows the effect caused by a change in timing and by delay dispersion of a radio channel on a signal received.
FIG. 2 shows two adjacent cells 1 and 2. Each cell is provided with a Base Transceiver Station BTS 1, resp.BTS 2. In this example, the Base Transceiver Stations have been connected to a controller of another Base Transceiver Station, BTS 1 to controller BSC 1, and BTS 2 to controller BSC 2, respectively. The controllers have been connected to an MSC which in addition to the controllers described controls a plurality of other Base Station Controllers. In a network used in the present invention, the timing difference between the Base Transceiver Stations BTS 1 and BTS 2 should be known. This is made feasible in that the network is entirely synchronous or at least partly synchronous.
An assumption is made in FIG. 2 first that a traffic connection exists between an MS and a Base Transceiver Station BTS 1. The Base Station BS 1 measures the signal power of MS during the connection and reports of it to the MSC when a handover is to be expected to a Base Transceiver Station subjected to a Base Station Controller BSC 2. In another instance the information is transmitted to the Base Station Controller BSC 1. The Mobile Station MS measures, according to the adjacent Base Station list received, periodically also the signal of the adjacent Base Station BSC 2 and reports BTS 1 thereof.
When the handover criterion is met, a report is signalled to Base Station Controller BSC 2 containing the parameters required in identifying an MS, and information about the frequency channel f2, the new time interval txs2 to be used, as well as the new frame number FN2. The controller guides the new Base Station BTS 2 to the channel directed by said information, and it is prepared to receive the incoming transmission from the MS. Thereafter, the MSC gives a command to the Base Station controller BSC 1 to control the Base Transceiver Station BTS 1 to transmit a handover command to MS containing said information already transmitted to Base Station BS2 about the new frequency channel f2, the new time interval txs2 to be used, and the new frame number FN2. Also the timing difference data between the Base Transceiver Stations is transmitted if the stations are not synchronized.
After receiving a handover command the MS sets the parameters (frequency, time interval, frame number) to correspond to the new location presented in the command, moves to a new channel and starts trafficking immediately, as well as delivers its identification data to a new Base Station BS2 which the new Base Station compares with the data provided by the MSC. In this manner the handover operation can be carried out very simply and rapidly.
The basic insight of the invention is to utilize the delay processing ability of the channel equalizer of the receiver to correct both the errors caused by the radio channel and the deviation caused by a change of the timing in a handover situation. The significance of the propagation delay and the delay dispersion regarding the channel corrector is illustrated in FIG. 3. The circles describe cells in the middle of which a Base Transceiver Station BTS 1 and BTS 2 are provided. For the sake of simplicity, the radius r of the cells is assumed to be the same. The following aspects are first defined:
t1 =the correction ability of the MS required in the system in the time level. This means variation of the reception point of time of a signal caused by a change of the timing and the delay profile.
t2 =the maximum delay dispersion of the radio channel determined for the network through which the Mobile Station has to pass. It is a given constant.
t3 =the maximum change of timing when moving from a Base Station to another. This value changes when the location of MS changes.
Such situations are examined in which the MS is in point A, point B and point C. When MS is in point A, t3 =0 is true because the distance to both Base Stations is the same. In point B, in which the MS is located adjacent to BTS 1, t3 is the time which the radio waves take when travelling between the Base Stations, i.e. t3 = 2 r/c, where c speed of light. As regards the handover, point B is difficult, but in practice no handover is carried out in this point, neither in point C. In point C the value of t3 lies somewhere between the values stated above. Thus, in points A and B the extreme values relative to t3 are obtained. According to the definitions the following details must become true:
t1 >=t2 +t3.
When t1 and t2 are those given in the system, it is found that at the same time they determine the maximum cell size of the network for the inequality to be true. In the reception of the Base Station the value of t3 can be considerably higher than in the reception of MS described above; therefore, the performance of the Base Station receiver has to meet higher requirements in this sense.
In FIGS. 4a and 4b an example is presented on the general principle of FIG. 3. Therein FIG. 4a, topmost, illustrates the impulse response of the channel in receiving a transmission from the Base Station BS1 of its own (or when the Base Station is receiving from MS). On the time axis, the space between two signs is the duration T of the symbol to be transmitted, dependent on the modulation speed and t2 is the length of the delay dispersion of the radio channel between its own Base Station BS1 and MS. The effect of said delay dispersion can easily be corrected with the channel corrector. The maximum time dispersion permitted by the channel corrector is marked with te. The delay components should be kept within said time dispersion also when moving to a new Base Station. The lower FIG. 4b is a corresponding presentation when the radio channel is placed between an adjacent Base Transceiver Station BTS 2 and the MS but the MS is within the timing of BTS 1. Now, t2 refers to the delay dispersion between MS and BTS 2. There is a timing difference t3 between the Base Stations, whereby the energy of the delay dispersion of the received symbol is visible in triangle form on the radio channel between Base Station BS2 and MS during the time t2. The delay profiles (i.e. triangles) are merely idealized assumptions, and the difference between the triangles illustrates only the fact that the radio channel can be different in the direction of different Base Stations. In practice the profiles can be highly indefinite. Let it be also mentioned that e.g. at bit speeds used in the GSM system, the duration of a symbol is equivalent to about one kilometer when presented as propagation distance. A cell of the size of one kilometer is already big e.g. in a cordless telephone network, and the delay dispersion need not necessarily be limited even to one symbol period, as is shown in FIG. 4a and b.
In the description of the invention as the one disclosed above, no attention is paid to the way of how the signalling is carried out between MS, BSC, BTS and the Mobile Services Switching Center. In the method of the invention the signalling need is small and, depending on the cellular telephone system applied, the channels and protocols used therein are applied in signalling. As is well known in the art, the identification of the MS can be transmitted with a contact specific control channel. If for one reason or another the signalling messages do not run between the telephone set and the Base Transceiver Stations, the telephone may try to return to the former channel, and if not even that attempt is successful, the call is interrupted.
The handover procedure simplifies the handover operation. A search of the synchronizing data from a Base Transceiver Station is not necessary, neither any heavy measuring and timing definition routines related thereto. When accomplishing a handover, nothing but the frequency, time interval, frame number data presented above are needed from the new Base Transceiver Station. For these reasons, the handover is rapid, and it has been simplified into a move from one channel to another. It is accomplished without any intermediate steps. The trafficing can be started directly via a new Base Station which has through the network been instructed to start listening to the MS moving thereon.
In view of the foregoing it will be clear to a person skilled in the art that modifications may be incorporated without departing from the scope of the present invention.
|Brevet cité||Date de dépôt||Date de publication||Déposant||Titre|
|US5042082 *||26 juin 1989||20 août 1991||Telefonaktiebolaget L. M. Ericsson||Mobile assisted handoff|
|US5081679 *||20 juil. 1990||14 janv. 1992||Ericsson Ge Mobile Communications Holding Inc.||Resynchronization of encryption systems upon handoff|
|US5241688 *||2 nov. 1992||31 août 1993||Motorola, Inc.||Frequency and time slot synchronizaton using adaptive filtering|
|US5247401 *||12 juin 1989||21 sept. 1993||Hitachi, Ltd.||Replay equalization circuit in digital image recorder|
|EP0214319A1 *||2 sept. 1985||18 mars 1987||ANT Nachrichtentechnik GmbH||Method for passing a mobile station from one radio station to another one|
|EP0324508A2 *||13 janv. 1989||19 juil. 1989||The Tokyo Electric Power Co., Inc.||Mobile communication system|
|EP0448015A2 *||18 mars 1991||25 sept. 1991||Fujitsu Limited||Mobile radio communication system|
|EP0474138A2 *||30 août 1991||11 mars 1992||Nokia Mobile Phones Ltd.||Timing logic for portable telephone in the GSM system|
|Brevet citant||Date de dépôt||Date de publication||Déposant||Titre|
|US5483668 *||22 juin 1993||9 janv. 1996||Nokia Mobile Phones Ltd.||Method and apparatus providing handoff of a mobile station between base stations using parallel communication links established with different time slots|
|US5523997 *||13 juin 1994||4 juin 1996||Motorola, Inc.||Communication network with dynamic intraswitching|
|US5566356 *||15 déc. 1994||15 oct. 1996||Nec Corporation||Mobile communication system and its multiple connection method enabling to perform concise and high quality multiplex communication|
|US5598459 *||29 juin 1995||28 janv. 1997||Ericsson Inc.||Authentication and handover methods and systems for radio personal communications|
|US5613205 *||31 mars 1995||18 mars 1997||Telefonaktiebolaget Lm Ericsson||System and method of locating a mobile terminal within the service area of a cellular telecommunication system|
|US5710974 *||15 mai 1996||20 janv. 1998||Nokia Mobile Phones Ltd.||Method for improving the reliability of a handover and call establishment, and a cellular radio system|
|US5711003 *||11 mai 1994||20 janv. 1998||Alcatel Mobile Communication France||Method for determining timing advance during handover|
|US5722074 *||24 sept. 1993||24 févr. 1998||Nokia Telecommunications Oy||Soft handoff in a cellular telecommunications system|
|US5749053 *||17 août 1995||5 mai 1998||Hitachi, Ltd.||Mobile communication network and control method thereof|
|US5754547 *||26 avr. 1996||19 mai 1998||Nec Corporation||Routing method and system using an internet protocol|
|US5774809 *||12 févr. 1996||30 juin 1998||Nokia Mobile Phones Limited||Simplified mobile assisted handoff of signal between cells|
|US5809399 *||5 janv. 1996||15 sept. 1998||Nokia Mobile Phones Limited||Method and circuit for filtering disturbances in a radio receiver|
|US5815801 *||15 mai 1996||29 sept. 1998||Nokia Mobile Phones Ltd.||Method for estimating the quality of a connection, and a receiver|
|US5825757 *||11 janv. 1996||20 oct. 1998||Nokia Mobile Phones Limited||Methods and apparatus for excluding communication channels in a radio telephone|
|US5828952 *||26 déc. 1995||27 oct. 1998||Motorola, Inc.||System and method for executing signalling cut-through|
|US5845192 *||4 avr. 1996||1 déc. 1998||Nokia Mobile Phones Limited||Wireless base station|
|US5862130 *||11 janv. 1996||19 janv. 1999||Nokia Mobile Phones Limited||Portable radio telephones and methods of operation|
|US5864759 *||30 juil. 1996||26 janv. 1999||Nokia Mobile Phones Limited||Radio telephones and methods of operation|
|US5870675 *||7 juin 1996||9 févr. 1999||Nokia Mobile Phones, Ltd.||Method for improving handover|
|US5896373 *||18 févr. 1997||20 avr. 1999||Nokia Mobile Phones, Ltd.||Method for executing handover in a radio extension of an ATM network|
|US5896570 *||4 févr. 1997||20 avr. 1999||Nokia Mobile Phones, Ltd.||Handoff by monitoring of received signal strengths among base stations|
|US5912885 *||18 févr. 1997||15 juin 1999||Nokia Mobile Phones Ltd.||Method for establishing radio connection as part of an ATM network|
|US5920547 *||23 juil. 1997||6 juil. 1999||Nokia Mobile Phones, Limited||TDD method between a base station and at least one mobile station|
|US5924038 *||16 mai 1997||13 juil. 1999||Nokia Mobile Phones Limited||Method and apparatus to speed up autonomous system selection after call release|
|US5940371 *||22 oct. 1996||17 août 1999||Nokia Mobile Phones Ltd.||Maintaining the composition of transferred data during handover|
|US5940743 *||5 juin 1997||17 août 1999||Nokia Mobile Phones Limited||Power control of mobile station transmissions during handoff in a cellular system|
|US5940760 *||16 mai 1997||17 août 1999||Nokia Mobile Phones Limited||Method and apparatus to reduce non-public mode search time in a mobile station|
|US5974036 *||24 déc. 1996||26 oct. 1999||Nec Usa, Inc.||Handoff-control technique for wireless ATM|
|US6002686 *||22 oct. 1996||14 déc. 1999||Nokia Mobile Phones Limited||Cell indication in the cell flow of an ATM system|
|US6108322 *||28 juin 1996||22 août 2000||Motorola, Inc.||Method of enabling handoff|
|US6115608 *||10 sept. 1997||5 sept. 2000||Northern Telecom Limited||Intersystem handover method and apparatus|
|US6119002 *||6 oct. 1997||12 sept. 2000||Nokia Mobile Phones Limited||Mobile station having methods and apparatus for performing neighbor channel measurements from analog control channel|
|US6122519 *||29 sept. 1998||19 sept. 2000||Nokia Mobile Phones Limited||Radio telephones and methods of operation|
|US6148207 *||5 févr. 1998||14 nov. 2000||Lucent Technologies Inc.||Optimization of FER settings during soft handoff|
|US6151314 *||22 oct. 1996||21 nov. 2000||Nokia Mobile Phones Ltd.||Use of header fields of an ATM cell in radio connected ATM data transfer|
|US6154455 *||24 déc. 1997||28 nov. 2000||Nokia Mobile Phones Limited||Prioritizing pilot set searching for a CDMA telecommunications system|
|US6178326||28 sept. 1998||23 janv. 2001||Nokia Mobile Phones Ltd.||Cell selection influenced by stored data and mobile station using same|
|US6201966||8 juil. 1998||13 mars 2001||Nokia Mobile Phones Limited||Allocating idle time to a mobile station|
|US6212173 *||14 févr. 2000||3 avr. 2001||Omnipoint Corporation||Communication system with fast control traffic|
|US6229996||12 déc. 1997||8 mai 2001||Nokia Mobile Phones Limited||Method and apparatus for increasing a probability that a dual-band mobile station will acquire a desired autonomous system|
|US6256304||31 mars 1998||3 juil. 2001||Nokia Mobile Phones, Limited||Mobile station using synchronization word order information for improved channel acquisition|
|US6272346 *||20 oct. 1998||7 août 2001||Nec Corporation||Manhole type base station, mobile communication system having the base station and hand-off control method in the mobile communication system|
|US6289006||5 juin 1997||11 sept. 2001||Nokia Mobile Phones Limited||Method and apparatus for changing carrier frequencies in each time slot in a telecommunications process|
|US6308066||7 janv. 1998||23 oct. 2001||Nokia Mobile Phones, Ltd.||Method to determine neighbor cell data in a mobile cellular system and a mobile station|
|US6310867||19 janv. 1999||30 oct. 2001||Nokia Mobile Phones Limited||Portable radio telephone and methods of operation|
|US6385451||13 sept. 1999||7 mai 2002||Nokia Mobile Phones Limited||Handover between mobile communication networks|
|US6400946||8 mars 1996||4 juin 2002||Nokia Mobile Phones Limited||Multimode universal mobile telecommunications system|
|US6434130||19 août 1998||13 août 2002||Nokia Mobile Phones Limited||Switching control method and apparatus for wireless telecommunications|
|US6470024||28 avr. 1999||22 oct. 2002||Nokia Mobile Phones Limited||Method and apparatus for controlling the use of idle frames|
|US6507570||14 mai 1999||14 janv. 2003||Nokia Mobile Phones Limited||Interfrequency measurement|
|US6507590||8 juil. 1997||14 janv. 2003||Nokia Mobile Phones Ltd.||Method of data transfer and data interface unit|
|US6510146||23 juin 1998||21 janv. 2003||Nokia Mobile Phones Ltd.||Method for handover and cell re-selection|
|US6510319||5 févr. 1998||21 janv. 2003||Lucent Technologies Inc.||Method for optimizing forward link power levels during soft handoffs in a wireless telecommunications network|
|US6532223 *||28 sept. 1998||11 mars 2003||Sony Corporation||Communication method, transmission method, reception method, base station and terminal|
|US6574473||8 mai 1998||3 juin 2003||Nokia Mobile Phones, Ltd.||Method and system for controlling radio communications network and radio network controller|
|US6574475 *||26 août 1999||3 juin 2003||Nec Corporation||Mobile communication system capable of performing soft-handover between base station controllers connected to different mobile communication exchanges|
|US6574485||30 mai 2000||3 juin 2003||Nokia Corporation||Power control in a radio system|
|US6577607||18 déc. 1997||10 juin 2003||Nokia Mobile Phones, Ltd.||Network structure for realizing part of a wireless ATM system and method for executing inter-switch handover in said network structure|
|US6577611||27 mai 1998||10 juin 2003||Nokia Mobile Phones Limited||Methods and apparatus for excluding communication channels in a radio telephone|
|US6580699 *||27 mars 2000||17 juin 2003||Nortel Networks Limited||Method for updating an R-P connection for a roaming mobile station|
|US6590880 *||15 oct. 1999||8 juil. 2003||Nokia Corporation||Apparatus, and associated method, for facilitating communication handover in packet radio communication system|
|US6603977 *||4 févr. 2000||5 août 2003||Sbc Properties, Lp||Location information system for a wireless communication device and method therefor|
|US6628630 *||13 avr. 1998||30 sept. 2003||Matsushita Electric Industrial Co., Ltd.||Spread spectrum communication method|
|US6628642 *||25 août 1999||30 sept. 2003||Telefonaktiebolaget Lm Ericsson (Publ)||Synchronization deviation detection|
|US6628941 *||29 juin 1999||30 sept. 2003||Space Data Corporation||Airborne constellation of communications platforms and method|
|US6662014||4 févr. 2000||9 déc. 2003||Sbc Properties, L.P.||Location privacy manager for a wireless communication device and method therefor|
|US6671283||18 déc. 1997||30 déc. 2003||Nokia Mobile Phones Ltd.||Method for flexible use of a tree topology in a wireless ATM system|
|US6757271||6 août 1999||29 juin 2004||Samsung Electronics Co., Ltd.||Method for providing a data service in a CDMA communications system|
|US6768908 *||7 avr. 2000||27 juil. 2004||Motorola, Inc.||Method and apparatus for soft handoff communications in a communication system operating according to IS-95B and IS-95C standards|
|US6788952||30 déc. 1998||7 sept. 2004||Nokia Mobile Phones Limited||Cell selection and reselection in a multiple modulation cellular radio system|
|US6961584||21 mars 2001||1 nov. 2005||Mlr, Llc||Tiered wireless, multi-modal access system and method|
|US6999765||22 sept. 2003||14 févr. 2006||Nec Corporation||CDMA type mobile station having first and second receiving portions for rounding off a chip offset temporally early and late|
|US7050771||16 avr. 2001||23 mai 2006||Nokia Corporation||Method and apparatus for increasing a probability that a dual-band mobile station will acquire a desired autonomous system|
|US7099625||7 juil. 1999||29 août 2006||Nec Corporation||Automobile communications method and system|
|US7187949||15 mai 2001||6 mars 2007||The Directv Group, Inc.||Multiple basestation communication system having adaptive antennas|
|US7190944||28 déc. 2001||13 mars 2007||Electronics And Telecommunications Research Institute||Method for performing handover based compressed mode and common frequency of neighbor cells|
|US7190952 *||3 oct. 2005||13 mars 2007||Hitachi Communication Technology, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US7194258 *||3 oct. 2005||20 mars 2007||Hitachi Communication Technology, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US7251226||9 nov. 2001||31 juil. 2007||Intel Corporation||Communication system with fast control traffic|
|US7254392 *||23 févr. 2001||7 août 2007||Nokia Corporation||Intersystem handover with modified parameters|
|US7274934 *||20 févr. 2002||25 sept. 2007||Commil Usa Llc||Wireless private branch exchange (WPBX) and communicating between mobile units and base stations|
|US7310519||19 janv. 2005||18 déc. 2007||Hitachi Communication Technologies, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US7406310||11 juil. 2006||29 juil. 2008||Hitachi Communication Technologies, Ltd.||Network management apparatus and method of selecting base station for software update|
|US7447497 *||8 août 2003||4 nov. 2008||Hitachi Communication Technologies, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US7454210||4 avr. 2003||18 nov. 2008||Nokia Corporation||Control of radio communication network having plural radio network controllers including an anchor controller|
|US7489942||4 févr. 2004||10 févr. 2009||Motorola, Inc.||Method and apparatus for soft handoff communications in a communication system operating according to IS-95B and IS-95C standards|
|US7512405||14 oct. 2003||31 mars 2009||Sbc Properties, L.P.||Location privacy manager for a wireless communication device and method therefor|
|US7606555||3 juin 2003||20 oct. 2009||At&T Intellectual Property 1, L.P.||Location information system for a wireless communication device and method therefor|
|US7627340||21 janv. 2008||1 déc. 2009||Mlr, Llc||Tiered wireless, multi-modal access system and method|
|US7640013||14 sept. 2007||29 déc. 2009||Hitachi Communication Technologies, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US7647039||15 mai 2007||12 janv. 2010||Hitachi Communication Technologies, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US7668147||27 mai 2003||23 févr. 2010||Intel Corporation||Communication system with fast control traffic|
|US7720472||14 sept. 2000||18 mai 2010||The Directv Group, Inc.||Stratospheric-based communication system having interference cancellation|
|US7729702||20 oct. 2008||1 juin 2010||Nokia Corporation||Method and apparatus for combining macrodiversity spread code signals|
|US7751808||14 oct. 2008||6 juil. 2010||Hitachi, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US7773981||14 oct. 2008||10 août 2010||Hitachi, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US7801522||13 nov. 2006||21 sept. 2010||Space Data Corporation||Unmanned lighter-than-air safe termination and recovery methods|
|US7809403||15 mai 2001||5 oct. 2010||The Directv Group, Inc.||Stratospheric platforms communication system using adaptive antennas|
|US7890122||2 févr. 2009||15 févr. 2011||At&T Intellectual Property I, L.P.||Location privacy manager for a wireless communication device and method thereof|
|US7929984||12 janv. 2007||19 avr. 2011||The Directv Group, Inc.||Multiple basestation communication system having adaptive antennas|
|US7937078||14 nov. 2008||3 mai 2011||Hitachi, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US7937079||16 juin 2010||3 mai 2011||Hitachi, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US7974630 *||9 mai 2000||5 juil. 2011||Nokia Corporation||Releasing a connection in a wireless communication network|
|US8078221||11 nov. 2009||13 déc. 2011||Mlr, Llc||Tiered wireless, multi-modal access system and method|
|US8081961||14 avr. 2008||20 déc. 2011||Hitachi, Ltd.||Network management apparatus and method of selecting base station for software update|
|US8204493||29 nov. 2010||19 juin 2012||Hitachi, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US8285270||25 mars 2011||9 oct. 2012||Hitachi, Ltd.||Wireless communication apparatus, wireless communication network and software upgrading method|
|US8396513 *||15 mai 2001||12 mars 2013||The Directv Group, Inc.||Communication system for mobile users using adaptive antenna|
|US8401559||12 déc. 2011||19 mars 2013||Mlr, Llc||Tiered wireless, multi-modal access system and method|
|US8700041||15 mars 2013||15 avr. 2014||Mlr, Llc||Tiered wireless, multi-modal access system and method|
|US8730881 *||26 déc. 2008||20 mai 2014||China Academy Of Telecommunications Technology||Method, system and apparatus for implementing cell handover|
|US8825232||1 févr. 2013||2 sept. 2014||Space Data Corporation||Systems and applications of lighter-than-air (LTA) platforms|
|US8831617||18 déc. 2013||9 sept. 2014||Mlr, Llc||Tiered wireless, multi-modal access system and method|
|US9519045||29 août 2014||13 déc. 2016||Space Data Corporation||Systems and applications of lighter-than-air (LTA) platforms|
|US9532267||8 sept. 2014||27 déc. 2016||Mobile Data Off-Loading Inc.||Tiered wireless, multi-modal access system and method|
|US9632503||1 déc. 2016||25 avr. 2017||Space Data Corporation||Systems and applications of lighter-than-air (LTA) platforms|
|US20020128044 *||15 mai 2001||12 sept. 2002||Chang Donald C.D.||Communication system for mobile users using adaptive antenna|
|US20020128045 *||15 mai 2001||12 sept. 2002||Chang Donald C. D.||Stratospheric platforms communication system using adaptive antennas|
|US20020164991 *||20 févr. 2002||7 nov. 2002||Commil Ltd||Wireless private branch exchange (WPBX) and communicating between mobile units and base stations|
|US20030117995 *||23 févr. 2001||26 juin 2003||Siemens Aktiengesellschaft||Method, mobile radiotelephone system, and station for determining a timing advance for a connection between two stations|
|US20030157935 *||23 févr. 2001||21 août 2003||Timo Kauhanen||Intersystem handover with modified parameters|
|US20030190915 *||4 avr. 2003||9 oct. 2003||Mika Rinne||Method and system for controlling radio communications network and radio network controller|
|US20030206530 *||27 mai 2003||6 nov. 2003||Lindsay Charles L.||Communication system with fast control traffic|
|US20040033795 *||3 juin 2003||19 févr. 2004||Walsh Patrick J.||Location information system for a wireless communication device and method therefor|
|US20040053615 *||28 déc. 2001||18 mars 2004||Il-Gyu Kim||Method for performing handover based compressed mode and common frequency of neighbor cells|
|US20040056852 *||22 janv. 2003||25 mars 2004||Jun-Ren Shih||Source driver for driver-on-panel systems|
|US20040057396 *||22 sept. 2003||25 mars 2004||Nec Corporation||CDMA type mobile station having first and second receiving portions for rounding off a chip offset temporally early and late|
|US20040128095 *||10 août 2001||1 juil. 2004||Stefan Oestreich||Adaptation of the timing advance in synchronous handover|
|US20040131036 *||14 oct. 2003||8 juil. 2004||Walsh Patrick Jay||Location privacy manager for a wireless communication device and method therefor|
|US20040157609 *||4 févr. 2004||12 août 2004||Louay Jalloul||Method and apparatus for soft handoff communications in a communication system operating according to IS-95B and IS-95C standards|
|US20040216099 *||8 août 2003||28 oct. 2004||Koichi Okita||Wireless communication apparatus, wireless communication network and software upgrading method|
|US20050141452 *||16 févr. 2005||30 juin 2005||Jan Vancraeynest||Base station for facilitating handover in TDMA communications|
|US20050208944 *||19 janv. 2005||22 sept. 2005||Koichi Okita||Wireless communication apparatus, wireless communication network and software upgrading method|
|US20060030308 *||3 oct. 2005||9 févr. 2006||Koichi Okita||Wireless communication apparatus, wireless communication network and software upgrading method|
|US20060030325 *||3 oct. 2005||9 févr. 2006||Koichi Okita||Wireless communication apparatus, wireless communication network and software upgrading method|
|US20070021116 *||11 juil. 2006||25 janv. 2007||Koichi Okita||Network management apparatus and method of selecting base station for software update|
|US20070218887 *||15 mai 2007||20 sept. 2007||Koichi Okita||Wireless communication apparatus, wireless communication network and software upgrading method|
|US20080064384 *||14 sept. 2007||13 mars 2008||Koichi Okita||Wireless communication apparatus, wireless communication network and software upgrading method|
|US20090042554 *||14 oct. 2008||12 févr. 2009||Koichi Okita||Wireless communication apparatus, wireless communication network and software upgrading method|
|US20090042578 *||20 oct. 2008||12 févr. 2009||Nokia Corporation||Method and system for controlling radio communications network and radio network controller|
|US20090111450 *||14 oct. 2008||30 avr. 2009||Koichi Okita||Wireless communication apparatus, wireless communication network and software upgrading method|
|US20090111451 *||14 nov. 2008||30 avr. 2009||Koichi Okita||Wireless communication apparatus, wireless communication network and software upgrading method|
|US20090137231 *||2 févr. 2009||28 mai 2009||Sbc Properties, L.P.||Location privacy manager for a wireless communication device and method thereof|
|US20100322118 *||26 déc. 2008||23 déc. 2010||Jiayi Fang||Method, system and apparatus for implementing cell handover|
|US20110070875 *||29 nov. 2010||24 mars 2011||Koichi Okita||Wireless communication apparatus, wireless communication network and software upgrading method|
|USRE42697||30 avr. 2008||13 sept. 2011||Mlr, Llc.||Apparatus and methods for networking omni-modal radio devices|
|USRE42921||2 août 2004||15 nov. 2011||Lg Electronics Inc.||Copy prevention method and apparatus for digital video system|
|WO2000019635A1 *||16 sept. 1999||6 avr. 2000||Nokia Networks Oy||Power control in a radio system|
|WO2001072015A1 *||21 mars 2001||27 sept. 2001||Leedom Charles M Jr||A tiered wireless, multi-modal access system and method|
|WO2002058279A1 *||28 déc. 2001||25 juil. 2002||Electronics And Telecommunications Research Institute||Method for performing handover based compressed mode and common frequency of neighbor cells|
|Classification aux États-Unis||370/331, 455/439, 370/337, 375/230|
|25 juin 1993||AS||Assignment|
Owner name: NOKIA MOBILE PHONES LTD., FINLAND
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KESKITALO, ILKKA;REEL/FRAME:006636/0818
Effective date: 19930610
|23 févr. 1998||FPAY||Fee payment|
Year of fee payment: 4
|7 févr. 2002||FPAY||Fee payment|
Year of fee payment: 8
|22 mars 2006||REMI||Maintenance fee reminder mailed|
|6 sept. 2006||LAPS||Lapse for failure to pay maintenance fees|
|31 oct. 2006||FP||Expired due to failure to pay maintenance fee|
Effective date: 20060906